1. Field of the Invention
The present invention relates to a chemically amplified photoresist composition, and more particularly, to a chemically amplified photoresist composition composed of a silicon-containing polymer compound.
2. Description of the Related Art
As semiconductor devices become highly integrated and complicated to manufacture, fine pattern formation is required. Accordingly, there is a great demand for new photoresists to be used in photolithography. Further, as the capacity of a semiconductor memory device exceeds 1 Gbit, a new photoresist material capable of being developed into a sharp pattern after exposure by an ArF excimer laser (193 nm) is necessary.
A photoresist that is intended for use with an ArF laser may be either a single layer resist (SLR) or a bi-layer resist (BLR), depending on the semiconductor fabrication process. Generally, the photoresist patterning process is simpler using an SLR than using a BLR. However, there are many problems associated with using an SLR. Foremost among them is the low dry etch resistance of the SLR. Another problem with SLR is the collapse of patterns having a high aspect ratio.
Although the patterning process is more complicated when a BLR is used, the BLR has a significantly higher dry etching resistance than the SLR due to the presence of silicon in the photoresist. During dry etching by O.sub.2 plasma, the silicon atoms in the BLR material crystallize into glass to form a hard layer over the surface of the photoresist layer. This hard layer acts as an etching mask during subsequent dry etching, thereby permitting the formation of a sharp pattern even if the aspect ratio is high.
The content of silicon in a polymer that is to be used in a photoresist composition is an important factor in fabricating the BLR. One example of a silicon containing polymer used in a bi-layer photoresist intended for use in an ArF excimer laser lithography process, is disclosed in Akiko Kotachi et al., "Si-containing Positive Resist for ArF Excimer Laser Lithography", J. Photopolymer Science and Technology, Vol. 8, No. 4, p 615, 1995. However, the silicon content in the polymer disclosed in the above reference, poly (TMSMMA-RMA), is only about 8 wt %. It is recognized that a silicon content of at least 10 wt % is necessary to attain a high enough aspect ratio, therefore the conventional silicon-containing polymers are not adequate to provide the high dry etching resistance that is required to form a sharp photoresist pattern at the high aspect ratio. Further, the silicon polymer described in Kotachi et al. for use with an ArF excimer laser in photolithography has inadequate adhesion characteristics, which means that the resist layer formed using the polymer may lift from the underlying layer, thus forming a photoresist pattern that is not sharp enough.